Get people in the habit of proactively updating at least daily. It isn't that hard to get them to do it. And it means that the possibility of conflict is addressed early and often. And if you choose not to do this you mainly create problems for yourself. :-)
For porting, create a branch and then run a command to detect conflicts every day. Similarly if you suspect that developers are not keeping good habits, you can run a cron job to find conflicts so you can come by and give them the speesh.
It can work. Many groups make it work for them. Bad developers can make it really suck, but they can do the same with any other source control system as well...
Cheers,
Ben